Calf housing design
There are five key requirements for a calf shed:
- Good ventilation to ensure air is fresh and no draughts are created.
- Adequate space: It is recommended to provide 2.0-2.3 m2 pen area per calf.
- Dry/good drainage: Calves spend 80% of their time lying down so they need a dry bed.
- Warmth: Calves perform best at 15-20oC; however, well-bedded calves are comfortable down to about 8°C.
- Clean and cleanable: Floors and walls should be easily cleaned
- Common problems associated with calf housing
Good ventilation takes away moisture, dust, ammonia, bugs and excess heat. It also kills harmful organisms living in the air – viruses for example will survive for a shorter time in fresh air than in stale air. Dust and ammonia irritate the respiratory tract and make the animal more vulnerable to respiratory disease. The recommended minimum air inlet and outlet per calf is 0.08 m2.
Natural ventilation is used in the vast majority of calf houses. This works in two ways:
- ‘Stack effect’: this occurs where warm air rises and leaves the building through an opening in the ridge and it is replaced by cooler, fresher air. The recommended roof slope of 15 to 22 degrees is a major help to the stack effect.
- ‘Wind effect’: in this case wind drives fresh air through the building.
Natural ventilation works best when the calf house is positioned at right angles to the prevailing wind and the building is not excessively wide (ideally <12 metres) or excessively high (3.35 to 4 m at the eaves is recommended).
Air inlets can be provided by ‘Yorkshire boarding’, space boarding or vented sheeting (Figure 1). Yorkshire boarding has two staggered lines of vertical timber so it reduces air speed, water entry and the likelihood of draughts. Specification S101 from the Department of Agriculture, Food and the Marine (DAFM) stipulates that the minimum length of the boarding is 1.5 m that the laths are 25 mm thick, a maximum width of 75 mm with gaps of at least 25 mm. The two lines of laths are 25 to 50 mm apart.
Space boarding can be satisfactory on the sheltered side of a calf house in a suitable site. If in doubt use Yorkshire boarding because wind direction can change and calves are sensitive to draughts. A draught is essentially excessive air movement (air speed >0.5m/s) at calf level. A capped ridge outlet is recommended with flashing, as required, to prevent wind driven rain getting in. Two alternative designs are shown below (Figures 2 and 3). An adequate roof slope will ensure that the outlet is at least 1.5m above the inlet.
Figure 1. Space boarding on left, and Yorkshire boarding on the right
Figure 2. Protected ridge with upstands
Figure 3. Covered open ridge
Ventilation fans can draw fresh air from outside the building and blow it through a plastic duct with numerous small outlets along the length. This system supplements or substitutes for inadequate air inlets.
It is recommended to provide 2.0-2.3 m2 pen area per calf. Typically, an individual pen must be 1.0 m wide by 1.5 m long, but 1.7 m is recommended, especially for isolation pens.
Calves spend about 80% of their time lying down so they need a dry bed. A dry environment will also reduce the spread and growth of bugs. All calf houses should be built with a damp-proof course to prevent rising dampness.
A slope of 1:20 in the calf pen area is recommended (Specification S124 DAFM). A split drain has the advantage that it will get urine and associated smells out of reach of calves quickly.
Calves perform best at 15-20oC but don’t generate sufficient heat to insulate themselves from colder temperatures until after they are weaned. Deep beds of straw are effective in protecting calves from the cold. Calves require 15-20 kg straw as bedding per week equivalent to one 150 kg round bale of barley straw to rear each calf. Well-bedded calves are comfortable with ambient temperatures as low as about 8°C.
Floors and walls should be easily cleaned. Floors can be laid in bays of not more than 4.5m by 6m to avoid the need to make contraction joints. Concrete floors that are well-compacted need to be well-cured to avoid plastic shrinkage cracks etc.
Natural light is conducive to good animal health and provides for a good working environment. It is recommended that 15% of the roof area should be translucent sheets (as listed on DAFM S.102).
Calf shed layout for different feeding systems
Figure 4 shows a suitable shed layout when calves are to be reared on an automatic calf feeder. Approximately 3.5 m of the pen is not bedded. This facilitates a reduction in straw usage and normal social behaviour among calves. Placing the split drain about 3 metres from the front of the pen helps to divide the fall across the shed (a 1:20 fall can be hard to achieve in practise). This area will, however, have to be cleaned at least daily, preferably with a ‘hand yard scraper’ since any use of water within the building should be kept to a minimum to keep down humidity. Three training pens, each capable of holding 3 small calves are included. A store with its own air space and access point to receive a pallet of milk replacer is provided (as recommended by DAFM specification S124). Two of the calf pens have small doors to allow calves access to a field, if desirable.
Figure 4. Calf shed suitable for an automatic calf feeder
Cold or draughty calf house
This can be a problem with some new calf houses that have high eaves or excessive ventilation. It can also occur when high sheds such as hay sheds are converted into calf houses. There is a delicate balance between having adequate ventilation while avoiding a cold uncomfortable environment for calves. Draughts can also occur with changes in wind direction, when doors are left open etc.
Prevention of draughts:
- Avoid excessive eave height over 4 m.
- Provide appropriate inlet ventilation on the ‘long’ axis of the building (in general not on gable ends).
- The use of a ‘protected ridge’ will prevent downdraughts from the outlet.
- Use ‘Yorkshire boarding’ or equivalent to dampen air speed especially on exposed sites.
- A high-standard of construction such as carefully fitted doors will help to prevent draughts at calf level.
The use of solid partitions between pens and a canopy at the back of the pens can help to create a comfortable environment for calves. This is equivalent to creating an ‘igloo-type’ environment within the calf house. The feedback from farmers who have used breathable washable calf jackets especially for young calves is positive.
- Extra calf housing
- Allow calves external space
- Early turnout to pastureby letting calves out by day - with shelter
- Repairing channels and using extra straw can help
- Redo floors with correct slopes, channels etc
Get further information on calf housing design
Teagasc, Kildalton Agricultural College, Piltown, Co. Kilkenny